Thermostat



Patented June 1, 1943 THERMOSTAT Paul R. Lee, Mansfield, Ohio, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application August 17, 1940, Serial No. 353,021

6 Claims. (Cl. 297-15) My invention relates to thermostats and more particularly to adjustable bimetallic snap-acting thermostats.

An object of my invention is to provide a simple, rugged, eflicient, snap-acting bimetallic thermostat which has a calibrating or adjusting member independent of the bimetallic element.

A further object of my invention is to provide a snap-acting thermostat utilizing a three-legged bimetallic element which is resiliently attached to a supporting structure by a resilient member attached to the central leg only of such element.

Another object of my invention is to provide means for calibrating a thermostat having an inherently snap-acting bimetallic element by varying the position of the fixed end of such element.

Still another object of my invention is to provide calibrating means for an inherently snapacting bimetallic element which cooperates with only a portion of such element.

Other objects of my invention will eitherbe pointed out specifically in the course of the following description of a device embodyin y invention, or will be apparent from such description.

In the accompanying drawing,

Figure l is a top plan view of a thermostat embodying my invention,

Fig. 2 is a partial sectional and elevational view of the device shown in Fig. 1,

Fig. 3 is a side elevational view of a portion of the thermostatic structure embodying my invention, and

Fig. 4 is an end view of the device shown in Figs. 1 and 2, taken along line IV-IV of Fig. 1.

Referring to the accompanying drawing, in which like reference characters indicate like parts in the several figures, I show a thermostat Ill comprising a supporting structure l2 having a stationary contact 21, a bimetallic snap-acting element H carrying a cooperating contact 28, a resilient member l6 for attaching the element to the supporting structure l2 and an adjusting or calibrating member l8 engaging the resilient member It for adjusting the operating temperature of the bimetallic element.

adjusting member l8, as hereinafter described. In addition, apertures 24 and 26 are located within either end of the supporting structure 12 to receive suitable rivet like members, as hereinafter described.

The bimetallic element It is of an inherently snap-acting type and is formed in a well known manner, as described in United States Letters Patent No. 2,259,312, issued to P. R. Lee, on October 14, 1941, and assigned to the assignee of this invention. This bimetallic element comprises a centrally located longitudinal extending strip Ila separated by slots l5 from outer strips b, extending substantially parallel to the central strip Ma. The outer strips b are crimped so as to cause the structure to be flexed into an arcuate configuration, with the central uncrimped strip Ha thereof being of a difierent configuration than the remainder of the element.

It is to be understood, however, that, while a three-legged snap-acting bimetallic element is shown, any other inherently snap-acting member may be used in lieu thereof. The bimetallic member I4 is, in this instance, rigidly attached near, say, the fixed end thereof, to the supporting structure l2 through the use of the resilient member I 6 which is adapted to engage with or to be attached to one end of the central strip Ila,

" The supporting structure i2 is, in this instance, formed of any suitable insulating material such as more fully hereinafter described. A movable contact 28 is spot welded or brazed to the free end of the bimetallic member I! so as to move therewith.

The resilient member i6 is, in this instance, an elongated spring member which is slightly bent, say, along a transverse line I! intermediate the free end of such member and the bimetallic element H (see Fig. 3). In other words, the resilient member l6 and bimetallic element I4 in this instance do not form a straight line when in their free or unmounted position. The resilient member l6 has an outwardly extending relatively narrowed protruding portion 30 (see Fig. 1). The portion 30 of resilient member I6 is adapted to extend beneath the central strip a and is rigidly attached thereto by a suitable rivet 32. The resilient member I6 is thus attached to a point in the central strip Ha of such bimetallic element H. An aperture 33 is located within the central portion of the resilient member I6 and is adapted to be positioned above the raised portion 20 of supporting structure l2 in line with the aperture 24 passing therethrough. A suitable rivet 34 may then be passed through the apertures 24 and 32 and spun over to rigidly attach the resilient member [6 to the supporting structure I2. The bimetallic element I4, being' attached to the free end of the resilient member I6 is thus positioned substantially parallel to the supporting Structure I2 with the movable contact 28 located upon the free end of such element engaging stationary contact 21.

The resilient member I6 being bent along line shank portion 3| of the stationary contact 21 is adapted to pass through the aperture 26 and also to pass through a corresponding aperture in a suitable terminal strap 36. The lower end of the shank portion 3| of the contact 21 is then spun over tightly against the terminal strap 36 so as to rigidly attach the contact 21 and strap 36 to the supporting structure I2.

With the resilient member I6 being bent downwardly with respect to the main portion thereof when in its normal unmounted position, it follows that, after such resilient member is attached to the fiat topped portion 26 of supporting structure I2, the bimetallic element ll, being attached to the bent portion of the resilient member I6, will be biased downwardly or into a contact-engaging position.

The adjusting or calibrating member I8 is, in this instance, an elongated setscrew having a rounded point at its upper end. Such calibrating member is adapted to be threadedly positioned within the aperture 22 inthe supporting structure I2. The adjusting or calibrating member ID, because of the threaded engagement with the supporting structure I2 is capable of being run up against the lower surface of the resilient member I6 so as to predeterminedly alter or determine the amount of downward biasing action of such member upon the bimetallic element I4. In other words, the adjusting or calibrating member I8 is. adapted to change the opening temperature of the thermostat as such member is moved upwardly against. the spring I6. A suitable lock nut 36 is run upon the lower' portion of the setscrew adjusting member I8 so as to engage the lower surface of the supporting structure I2 and to lock such member in its predetermined set position. In other words, the adjusting calibrating member I6 is used primarily as a factory setting means'for determining the fixed opening temperature of the thermostat.

It will be noted that current through the thermostat III, when connected in or to a suitable circuit which it is desired that the thermostat conat which time the element I4 will snap or abruptly move to an upper or contact disengaged position (see dotted lines, Fig. 2); This upward snap-action of the bimetallic element occurs against the downward biasing action of the resilient member I6. With the upward fiexment of the element I4 the circuit passing therethrough is broken. The element I4 thus cools until reaching its predetermined closing temperature at which time the element, assisted by the downwardly biasing action of resilient member I6, will snap downwardly to the substantially parallel or I contact engaged position (see solid lines, Fig. 2).

trol, also traverses resilient member I6 and the terminal strap 36. The path of the current would then be substantially as follows: from, say, re-

silient member I6 to the bimetallic element I4,

through the rivet 32, the movable contact 26, stationary contact 21 and out through the terminal strap 36. Passage of current through the bi- The thermostat III will thus cycle back and forth within substantially fixed temperature limits.

It will be understood that the resilient member I6, as hereinabove described, through the action of adjusting member I6, permits the angular position of the bimetallic element to be selectively changed with respect to its point of support. The adjusting member I8 cooperating with the resilient member I6 thus changes the angular position of the so-called "fixed end of the bimetallic element ll, or that end attached to the resilient member I6, for the purpose of varying the opening temperature of the thermostat. It is, therefore, obvious that, by adjusting or varying the effective angular position of the fixed end of the bimetallic element, such element may be adapted to flex from a closed to an open position at various predetermined tem peratures.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and I desire,

therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

I claim as my invention:

1. A snap-acting device comprising, in combination, a supporting structure, a snap-acting bimetallic element including a central strip and two exterior strips'together with end portions (combination, a supporting structure, a snap-acting bimetallic element having a central strip and a movable and a relatively stationary and portion, means attached solely to the central strip of said element for movably attaching such element outside of its boundaries to the supporting structure, said stationary end portion contacting said means over a substantial area, and adjusting means cooperating with said first means for varying the angular position of said central strip and stationary end portion of said element for adjusting the operation of said element.

- 3. A snap-acting thermostat, comprising, in combination, a supporting structure, a bimetallic element having a central strip and two exterior strips joined by end portions, a resilient member rigidly attached to the central strip of said element for attaching the element outside of its boundaries to the supporting structure and for alone biasing the element into ,a predetermined position, and adjusting means engaging the resilient member for selectively adjusting the biasing action of said member and the operating temperature of said bimetallic element.

4. A snap-acting thermostat, comprising, in combination, a supporting structure, a bimetallic element including a central strip and two exterior strips, a resilient member rigidly attached to the central strip and secured to the supporting structure outside of the boundaries of said element {or alone biasing the element into a predetermined position, and adjusting means retained by the supporting structure engaging the resilient member independently of the bimetallic member for selectively adjusting the operating temperature of such bimetallic element.

5. A snap-acting thermostat, comprising, in combination, a supporting structure, a bimetallic element including a central strip and two exterior strips, and a resilient member rigidly attached to the central strip to constitute the sole place of support of said element and also attached outside of the boundaries of said element to the supporting structure for alone biasing the element into a predetermined position, and adjusting means retained by the supporting structure engaging the resilient member independently' of the bimetallic member for selectively varying the position of said place of support of the bimetallic element to adjust the operation of such element.

6. A snap-acting thermostat comprising, in combination, a supporting structure, a snapacting bimetallic element, resilient means rigidly attached to said element for securing it outside of its boundaries to the supporting structure, and adjusting means cooperating with said resilient means for varying the angular position of said element, said resilient means being biased towards a position of engagement with said adjusting means.

PAUL R. LEE. 

